Unprecedented Greenland Ice Sheet Surface Melt

Satellites See Unprecedented Greenland Ice Sheet Surface Melt

July 24, 2012: For several days this month, Greenland's surface ice cover melted over a larger area than at any time in more than 30 years of satellite observations. Nearly the entire ice cover of Greenland, from its thin, low-lying coastal edges to its two-mile-thick center, experienced some degree of melting at its surface, according to measurements from three independent satellites analyzed by NASA and university scientists.

On average in the summer, about half of the surface of Greenland's ice sheet naturally melts. At high elevations, most of that melt water quickly refreezes in place. Near the coast, some of the melt water is retained by the ice sheet and the rest is lost to the ocean. But this year the extent of ice melting at or near the surface jumped dramatically. According to satellite data, an estimated 97 percent of the ice sheet surface thawed at some point in mid-July.

Extent of surface melt over Greenland’s ice sheet on July 8 (left) and July 12 (right). Measurements from three satellites showed that on July 8, about 40 percent of the ice sheet had undergone thawing at or near the surface. In just a few days, the melting had dramatically accelerated and an estimated 97 percent of the ice sheet surface had thawed by July 12.

Researchers have not yet determined whether this extensive melt event will affect the overall volume of ice loss this summer and contribute to sea level rise.

"The Greenland ice sheet is a vast area with a varied history of change. This event, combined with other natural but uncommon phenomena, such as the large calving event last week on Petermann Glacier, are part of a complex story," said Tom Wagner, NASA's cryosphere program manager in Washington. "Satellite observations are helping us understand how events like these may relate to one another as well as to the broader climate system."

Son Nghiem of NASA's Jet Propulsion Laboratory in Pasadena, Calif., was analyzing radar data from the Indian Space Research Organisation's (ISRO) Oceansat-2 satellite last week when he noticed that most of Greenland appeared to have undergone surface melting on July 12. Nghiem said, "This was so extraordinary that at first I questioned the result: was this real or was it due to a data error?"

Nghiem consulted with Dorothy Hall at NASA's Goddard Space Flight Center in Greenbelt, Md. Hall studies the surface temperature of Greenland using the Moderate-resolution Imaging Spectroradiometer (MODIS) on NASA's Terra and Aqua satellites. She confirmed that MODIS showed unusually high temperatures and that melt was extensive over the ice sheet surface.

Thomas Mote, a climatologist at the University of Georgia, Athens, Ga; and Marco Tedesco of City University of New York also confirmed the melt seen by Oceansat-2 and MODIS with passive-microwave satellite data from the Special Sensor Microwave Imager/Sounder on a U.S. Air Force meteorological satellite.

The melting spread quickly. Melt maps derived from the three satellites showed that on July 8, about 40 percent of the ice sheet's surface had melted. By July 12, 97 percent had melted.

This extreme melt event coincided with an unusually strong ridge of warm air, or a heat dome, over Greenland. The ridge was one of a series that has dominated Greenland's weather since the end of May. "Each successive ridge has been stronger than the previous one," said Mote. This latest heat dome started to move over Greenland on July 8, and then parked itself over the ice sheet about three days later. By July 16, it had begun to dissipate.

Even the area around Summit Station in central Greenland, which at 2 miles above sea level is near the highest point of the ice sheet, showed signs of melting. Such pronounced melting at Summit and across the ice sheet has not occurred since 1889, according to ice cores analyzed by Kaitlin Keegan at Dartmouth College in Hanover, N.H. A National Oceanic and Atmospheric Administration weather station at Summit confirmed air temperatures hovered above or within a degree of freezing for several hours July 11-12.

"Ice cores from Summit show that melting events of this type occur about once every 150 years on average. With the last one happening in 1889, this event is right on time," says Lora Koenig, a Goddard glaciologist and a member of the research team analyzing the satellite data. "But if we continue to observe melting events like this in upcoming years, it will be worrisome."

Greenland ice sheet record surface melting underway

While the potential impact of wildfires on darkening the Greenland ice sheet surface remain to be resolved, there is mounting evidence of an extreme year 2012 melt.

Melt signatures from active microwave remote sensing are stronger than in recent years over the upper areas of the ice sheet. Dark areas indicate absorption of the microwave signal emitted by the satellite. While, year 2010 and 2011 are recognized as being record melt years (Tedesco et al. 2011, van As et al. 2011), year 2012 melting appears to be more extensive.

(...)

In my recently accepted albedo paper (Box et al. 2012, ACCEPTED VERSION), see abstract, the statement: “it is reasonable to expect 100% melt area over the ice sheet within another similar decade of warming.” may be coming true already.

Surprising Link Between Ice and Atmosphere: GPS Can Now Measure Ice Melt, Change in Greenland Over Months Rather Than Years

ScienceDaily (July 24, 2012) — Researchers have found a way to use GPS to measure short-term changes in the rate of ice loss on Greenland -- and reveal a surprising link between the ice and the atmosphere above it.

The study, published in the early online edition of the Proceedings of the National Academy of Sciences, hints at the potential for GPS to detect many consequences of climate change, including ice loss, the uplift of bedrock, changes in air pressure -- and perhaps even sea level rise.

The team, led by earth scientists at Ohio State University, pinpointed a period in 2010 when high temperatures caused the natural ice flow out to sea to suddenly accelerate, and 100 billion tons of ice melted away from the continent in only 6 months.

They were able to make the measurement because Earth compresses or expands like a spring depending on the weight above it, letting them use the Greenland bedrock like a giant bathroom scale to weigh the ice atop it. As ice accumulates, the bedrock sinks, and as the ice melts away, the bedrock rises.

Measurements revealed that Greenland sank by about 6 mm (about one quarter of an inch) over the winter of 2010, and the researchers determined that half of the sinking (3 mm, or one eighth of an inch) was actually due to high air pressure above the ice, and the other half was due to ice accumulation.

Further, they determined that the bedrock lifted 11 mm (less than half an inch) over the course the summer. Air pressure appeared to affect the bedrock less during this time, so that the bounce-back appears to be mostly due to ice loss.

(...)

While shortening the detection time to six months is a substantial advance, Bevis thinks his team will soon do even better.

"Within the next year or so, we should be able to process the GPS data within a month of its being collected," he said, "and then we can monitor abrupt changes in ice mass only a month or two after they occur."

(...)

Although this study revealed a dramatic six-month period of melting in Greenland in 2010, that short-term ice loss isn't necessarily a sign of a long-term trend, Bevis cautioned.

"It is dangerous to assume that rates observed over even two or three years reflect a long-term trend. Rates are known to change. So, it would be even more dangerous to assume that the record breaking summer of 2010 is the new norm."

"That being said, the summer of 2011 was also very hot. And this summer is starting off hot, too. So, I do expect to see a sustained increase in uplift rates when we compare 2010-2012 to 2007-2009," he added.

Comments

"I arrived at Summit Station on July 13th, while traveling with the
Joint Science and Education Program (JSEP) for a short visit to the
camp. When we arrived, Summit Station had been experiencing above
freezing temperatures for multiple days prior to our arrival and a
melt layer formed on the near surface snow. I have been studying the
physical properties of the top layers of the ice, the firn, at Summit
and NEEM for my Ph.D. research. Recently, I have been focused on the
melt layers present in both firn cores because they occur very
infrequently. At Summit, there is only one other melt layer besides
the melt layer from this past week and this previous melt layer dates
to 1889."

Be my guest, Dana. It's one big copypaste anyhow, so I don't see how you need my permission. :-)

Anthony Watts went into ultrafast downplay mode, so the forces of delay must be really displeased with this news. There's no need really. However, if it happens again within a lot less than 150 years...

If Greenland would keep exactly the same amount of ice over time, it would still be normal for objects to be covered with ice. Because Greenland would still lose ice all around its edges, new snow and ice on top of the old one - and any objects left there - would be needed to compensate the loss.

So one would have to check whether the gain by new ice outweighed the ice loss around the edges. It may well be the case that Greenland's ice mass indeed grew between 1942 and 1992, since it was generally a cooler era than the rapid warming era we have now (maybe due to all the sulfur in the air working against the greenhouse effect).

But if Greenland is losing albedo in an area, this means in this area ice was not gained but actually lost, because the ice covering the dust and soot had melted, allowing it to become denser, increase absorption and cause the albedo loss.

So independently of whether Greenland had gained ice in the last century, right now it's losing ice, and rapidly.

Does anybody know the evidence for this statement "Ice cores from Summit show that melting events of this type occur about once every 150 years on average"?

The ice core from Summit analysed by Kaitlin Keegan only goes back to 1750 and has just a single melt layer in 1889. Hardly sufficient information to say melt layers occur ever 150 years - a statement that the WUWT is using to claim that nothing unusual is happening. I have not been able to find archived data on melt layers on the long cores from Summit.

When will we know if this unusually widespread melt led to, or will lead to a change in mass balance?

How are the moulins and supraglacial lakes doing compared with previous years?

The recent video of the surging Watson River was fairly impressive, but how did its flow rate differ from the average for the time of year?

Was this representative of all rivers draining from the icesheet?

rayduray on Climate Crocks mentioned that the Watson River flow rate was 3.5 million litres per second - that's 3,500 x 86400 = 300 million tonnes per day, or nearly 1 km3 of water every 3 days! For just one river! Is this correct?

Multiply by the number of rivers and their relative flow rates, and it could be a truly awesome amount of melting this year.

The plane crashed in 1942 in 1992 was covered by nearly 100 meters of snow and ice.

Thus the plane has sunk for about 100 m deep into the ice.

After all, sinking, it's that what boulders and heavy objects do in moving ice fields, don't they?
The same reason why people fallen into a glacier reappear only 50-100 or even 150 years later at the tongue of a glacier.

It appears that best estimates of annual averages are perhaps closer to 250 m^3/s which is slightly smaller than the discharge from the Delaware River (330 m^3/s). This does not mean that peak discharges cannot reach much larger values, but a short pulse may not reflect the importance of this element in the mass balance of Greenland. My source is http://www.the-cryosphere.net/6/199/2012/tc-6-199-2012.pdf that I still have to read more careful than a 10 minute browse. I wonder if there are other gauged rivers around Greenland and if a scaling law exists that relates catchment area (and/or temperature and/or something) to discharge for land-based glaciers or ice sheets. I know such laws exist for mid-latitude rivers as well as Alaska's many streams and rivers ... but Greenland?

"The recent video of the surging Watson River was fairly impressive, but how did its flow rate differ from the average for the time of year?"

From what I've read, this event was a unique anomaly. The flow exceeded any previous flooding event by a factor of 2.

The huge flow of water was most likely due to glacial dam giving way and draining a significant body of trapped, hidden water. This happens with some frequency in Iceland, but has been rare in Greenland. A similar phenomenon has been studied in the western U.S. Glacial Lake Missoula http://en.wikipedia.org/wiki/Glacial_Lake_Missoula has been well-researched over the past few decades. Here's one of my favorite videos about these gargantuan flood events: http://www.youtube.com/watch?v=r1MNpYb5YCA

***
"Was this representative of all rivers draining from the icesheet?"

No. This was a unique situation. Of course in a warming world, we can expect more such unique events never before observed.

***
"rayduray on Climate Crocks mentioned that the Watson River flow rate was 3.5 million litres per second - that's 3,500 x 86400 = 300 million tonnes per day, or nearly 1 km3 of water every 3 days! For just one river! Is this correct?"

If you add in "surface" after "ice" the headline would be correct. But usually nobody cares about surface ice melting, just whether the main ice remains or melts, so somebody probably misunderstood the true content of the news.

Not sure sunk is the right word as it may imply going down faster than surrounding ice. Talk of boulders and heavy objects compounds this error. A plane is going to be light compared to ice.

Surely it is much more a case of add snow and ice above the object while ice below moves downhill.

.

GRACE tells us greenland is losing mass but when did GRACE start and how well did we know the mass balance between 1992 and GRACE start? If not very well, can we be sure there wasn't much change from river discharge rates or something?

Seeing glaciers retreat may well mean we knew there was mass loss around edges but did we know whether it might be outweighed by mass gain at high altitude?

Wipneus,
I seems that the Volkskrant realised their mistake.
They mellowed it out to :'Groot deel' bovenkant landijs Groenland aan het smelten
with the first line :Een gedeelte van de toplaag van het landijs op Groenland is half juli zo snel gesmolten dat onderzoekers van NASA...
Did Monckton or WUWT make a similar correction to their statements ?

The ice core from Summit analysed by Kaitlin Keegan only goes back to 1750 and has just a single melt layer in 1889. Hardly sufficient information to say melt layers occur ever 150 years - a statement that the WUWT is using to claim that nothing unusual is happening.

I second that opinion.
The Greenland ice sheet cores record more than 100,000 years of climatic history from the summit.
Did nobody analyse melting lines in these cores earlier than 1750 ?
If not, why not ?

"I second that opinion.
The Greenland ice sheet cores record more than 100,000 years of climatic history from the summit.
Did nobody analyse melting lines in these cores earlier than 1750 ?
If not, why not ?"

An hypothesis could be that "melting lines" are only visible in fresh, not fully transformed ice, i.e. only at the top of ice cores...

How will the cat in the hat clean up all of that pink? The impact of higher albedo and higher temps are reinforcing of each other. The result will be bigger impacts on the glaciers ending on land and small Greenland Ice Caps. Mernild et al (2012) has focussed on these. The area around De Reste Bugt Glacier emphasizes this too.

http://adsabs.harvard.edu/abs/2011AGUFM.C33C0661K
"A core from the CO2 firn-air sampling site at NEEM was retrieved in July 2009, and the physical properties of the firn have been analyzed. In the 81m of analyzed firn core, two regions containing ice layers were identified at depths of 29m and 46m. Isotopic analysis provides a depth-age scale that dates these layers to be from 1935 and 1879, respectively."

Dark objects on ice sink can even when they are "lighter" than the ice and even if there is no snowfall at all. Mechanism is that sun warms the object, and the water drains away under it or evaporates away from the margins. The density difference doesn't matter much with a solid you are melting your way into.

This is the paper that can put the '150 years' comment in proper context. See the figures. A significant amount of melt years occurred during the Mid-Holocene Optimum. The average over the last 4000 years is about every 250-300 years. This includes the MWP where seven of the last 8 occurred, meaning, before a few weeks ago 1889 was the only occurrence in the last 800-900 years or so. Dr. Alley's hypothesis is that these clusters of melts over 6000 years ago were do to high summer insolation.

One could presume that the 1.3C change in temp for June 2012 (or July) compared to the last century effected Greenland as well. This begins to place a perspective on the cooling vs melt frequency.

Now we revisit Alley's melt frequencies (in "Results")

Average for 0-10000 BP is 1/153 yrs.
Average for 5500-8500 BP is 1/82 yrs.
Average for 1000-4000 BP is 1/250 yrs.

If his melt frequency assumption for approx 7500 ka ago is based upon 1.3 C above the current temps - it seems we are negating that very quickly. That would seem to put us back to a potential 1/82 year occurence.

Perhaps it is more frequent - or will rapidly become more frequent. In his "Calibration" section for GISP2 with Site A melt data he mentions a statistical correlation for temp vs melt.

"Assuming that the summertime temperatures have the same standard deviation for GISP2 and site A over the study period, that standard deviation must be 3.5°C so that a 2°C increase in temperature causes a 7.5-fold increase in melt frequency, based on examination of standard statistical tables for the integral of the normal distribution."

While this dealt with temperature difference between two sites in relation to melt frequency - is it reasonable, or statistical to assume that the same ratio would hold for an increase in frequency for the same location with a 2 C increase in temperature over time?

It is not important to debate whether Dome melt as a singularity is exceptional, unprecedented or whatever. It happened before under natural variety.
What is important is the multi-year rise of melt rate for the GIS as a whole. This features a clear graph starting around 125 km3, varying around 250, topping at 550 during 2010 and this year on course for maybe 700. This may be hard to establish as unprecedented. But it isn’t hard to imagine where this is going under constant forcing and emerging feedback. The South Dome is under siege and prone to raise sea level. On the worst IPCC scenario path…

The historical data is based on ice layers in the firn (compacted snow). Therefore, to be distinguishable, you'd need significant snowfall to occur in between two melt periods, to produce distinct icy layers. I don't know what the resolution is, but it certainly won't be on the order of days, more likely years.

So, however many times the temperature goes above freezing this year, for comparison to the historical data we just have to call it a "melt year" and leave it at that, I think.

Put another way, I don't think the snowfall (if any) in the last 6 days will be suffcient to produce distinct layers if there's another melt episode (or two, or three) this year. In a century's time it'll just show up as one layer.

From the little while ago Rutgers snow *reasoned* anomaly from the observed on various maps and current developments, looking very much forward what they are going to report for cover in the weekly data for July. Not due out until later in first week of August.

Not even sure the NWP will open at all if McClure Strait doesn't get unblocked at the western end somehow, currently choked with heavy multiyear ice...

I was surprised to see on yesterday's satellite image that McClure Strait is actually almost free of ice. It's the eastern part of the NWP that seems to be the problem. If it is a problem, because the clouds are still blocking that portion. Either way, almost all of the ice seems to be melting in situ.

The Greenland ice sheet cores record more than 100,000 years of climatic history from the summit.
Did nobody analyse melting lines in these cores earlier than 1750

and then asked:

If not, why?

Well, for a starter you would need a 2 km deep drill right to the bottom of the ice shell. Which implies the need for heavy tools and materials, and above all a massive investment in money and resources.

It had been done at Antartica, a drill trough a 2 km thick ice layer to the surface of a frozen lake (a lake with a Russion name which I don't recall for now).

Obviously, the reasons for Russians and Americans to spend all that taxpayers money at Antartica come from a military-strategic scope, in order to claim as much territory as possible for a starter.

As the latter isn't feasible at Greenland, it's only about research and science there.
And far less of money available. (-:

The ice core from Summit analysed by Kaitlin Keegan only goes back to 1750 and has just a single melt layer in 1889. Hardly sufficient information to say melt layers occur ever 150 years - a statement that the WUWT is using to claim that nothing unusual is happening.

I second that opinion.
The Greenland ice sheet cores record more than 100,000 years of climatic history from the summit.
Did nobody analyse melting lines in these cores earlier than 1750 ?
If not, why not ?
Posted by: Rob Dekker | July 25, 2012 at 12:18

Hmm, not that misleading. For events occurring a century or more apart, you need to average over 1000 years or so to get an idea of the true average rate. Doing that, you see that over the last 4000 years, the 1000-year smoothed value has been hovering around 0.04, i.e. one melt year every 250 years. Sure, it's a bit longer than the stated 150, but it's close enough that it's not grossly misleading - and averaging over the whole historical record negates claims of cherry-picking.

The most accurate statement would be that melt years this intense are somewhere between a 1/250 year event and 1/60 year event, being more common during the Holocene optimum 6-8000 years ago when the Earth's orbital tilt favoured (local) Northern Hemisphere warming. But you won't fit that into a newspaper article >:-)

Jason Box provided a good graphic on his blog (links above) about the energy budget at the Greenland summit. It seems an increase of <1 w/m^2 was enough to nudge the summit into a melt. So with the solar cycle peaking in 2013, we will likely see another summit melt event next year.

Based on the data at Summit given in GISP2 the rate of occurrence there is ~15/4000 years, since it’s such a rare event it’s reasonable to model it as a Poisson process, with a λ of 0.375 (per century). Over the last 4000 years that’s a mean expectation of 0.375/century with a variance of 0.375. From a Poisson analysis you’d expect ~27 centuries without a melt, ~10 centuries with one melt year, ~2 centuries which is in reasonable agreement with the data. As usual with such data it's quite normal to see clustering, going further back doesn't make sense though because of the significant increase in insolation then.

"The great storm had its origin on the California coast on May 26. From the Pacific to the Atlantic seaboard, heavy rains accompanied the disturbance…. The storm had general characteristics which made it unusual for such an extensive change of weather. The storm moved at an unusually slow pace, and at a regular speed. High temperatures were shown in some areas; while low temperatures from frost to snow prevailed in others. Local storms in this vast cyclonic movement were unusually violent. Saturation was dense and rainfall enormous.

A pressure area over the Atlantic Ocean turned the winds to a south-to-east direction although they usually moved from south to west. The changed direction of the ocean winds, coupled with the normal west-to-east movement of the storm current, forced the winds with their huge rainfall into a comparatively small area over the crest of the Alleghenies, –three low pressure areas from the west, southwest, and southeast “met in a dire embrace upon the summits of the Allegheny mountains.”"

"This past March was the second warmest winter month ever recorded in the Midwest, with temperatures 15 degrees above average. The only other winter month that was warmer was December of 1889, during which temperatures were 18 degrees above average. Now, MU researchers may have discovered why the weather patterns during these two winter months, separated by 123 years, were so similar...."

I didn't give it much thought, as I figured it was entirely irrelevant to the event itself, but now that I have thought about it, I find it amazing that Koenig has said this and even more amazing that the people over at NASA put this quote in. They handed the fake skeptics everything they needed to mislead and obfuscate on a silver platter.

The melt event is a signature event, but short term. The longer term issue of ice sheet mass balance for 2012 is indicated by the extent of bare ice, as this is the best single indicator of overall mass balance annual variation. Notice the bare ice graph, fourth down from Xavier Fettweis's lab.

Yes the fast ice in Jøkelbugt is on the move now, it is the first time since 2004 - 5 I believe, it is not happening each year, normally this fast ice dont block the "Fram Export", and the Fram situation has been very stationary for the last 2 weeks.
It will be interesting to watch if there are any reactions from the 2 Giant Glacier 79th and Zachariae, since there is no sea/fast ice to stop an eventually calving. This area (Jeokelbugt) is probably also where you will find the biggest differences of many since 2007, so I will suggest you to watch this area for next month, there could some big actions!

Yes I know the ice breaks up in the area, but not this early, you are comparing day 248 with day 213, and the result last year was the ice stayed as it normally do, but this year I am pretty sure it will be far a way in the sea somewhere on day 248.

Apparently a warm summer like this year has implications for the formation of ice out of firn/snow. The assumptions, with which actual measurements are calculated into reliable mass balance estimates, have to be renewed.
Other subjects announced for the meeting will be informative too. Like new research op surface height change, the effect of micro-organisms on the ice etc.
To have a clear view on the relevance of this summers melt, it would be great when a presentation on actual mass balance will be presented at the AGU meeting.

Meanwhile, I’m working on the MODIS day 191-196 tiles on Greenland. I chose the days because snow/cloud cover looked to be at minimum.
I’m trying to define/CAD the ice boundary at that time. It is a hell of a task, I’ve spent about 30 hours on it and have app. another 20% to do. While it could give a quite good area calculation, it will also enable to make out differences with the other 3 available years.

Eyeballing hasn’t got me very far. I hope this work will provide a basic insight whether a geographically noticeable retreat has started.
If so, and combined with what’s already published on mass loss, it would be another sign that icesheets react quickly to climate change. And that any arguement like the melt process would take at least hundreds of years are irrelevant in today’s circumstances.

Found this: http://imbie.org/imbie-2012/results/
What is scary is that the curve of the charts at the bottom seem to following a similar trend as to the collapse of the Arctic Ice. This also shows beyond question that what is happening in the Antarctic is not the ice extent, but the ice balance. Not only that, I believe that although the East is looking great for now, it is hiding the fact that although still very cold is in fact warming and once it hits that magic temp will collapse there also.

For what its worth... I finally fixed the outer boundary of the icesheet in CAD on the MODIS tiles.
I know...it looks a bit 'pale', but I just wanted to share this baby of mine with you.
Some first data: the line is 55.790 km1 long (my...I digitized 173.761 points in the polyline). The area is 1.793.564 km2.

I'm off to get some sleep, but I'll be back on this when I find time to compare this to the earlier years.

I couldn’t wait to get the corresponding 2009 MODIS tiles under the CAD-digitalized ice/snow-limit 10-14 July 2012 polyline.
I’m planning to put specific info on a map. That will take some time, so here is a first general impression.

On the South-Southwest there’s noticeable retreat. That goes for most glacierfronts (200-1500 m) as well as for the snow/ice limit on the fjells and around the nunatakkers (average about a pixel-width; 200-300 m).

The mountainous east side holds steady. There are even some glacierfronts that have extended. A part of the coast between Tasiilaq and Scoresbysund even had less snow and remaining landfast ice in July '09 than last July.

The North is also steady. No surprise that Peterman Glacier stands out, but so does loss on the Humboldt and some other, smaller outlet glaciers.

I feel relieved that the retreat looks not as bad as in my worrisome musings.

Nevertheless, the progressive retreat in SW Greenland is considerable.
On the mountain ridge in the SE there could be some snow accumulation, but not enough to compensate.

There’s FI the melt zone to investigate further, which could tell something about the lowering of the sheet surface. For now, what I found fits well with the mean average mass balance totals for the last three years and the supposed big 2012 loss. Relatively big. There’s still an incredible lot of ice out there.

Oh yes. I have to add some of the restrictions I made while digitalizing.

I took the limit of consistent snow/ice. That left out stand-alone icecaps, like FI Fade Isblink.
The same goes for inside ice/snowfree ‘polynia’s’. There are a d***** lot of nunatak strikes in the mountainous parts and some large ice/snowfree landscapes within the sheet north of Scoresby Sound.

To add some more info on the posts above, I have roughly calculated the margins min/max for what is supposed to be the large 2012 mass loss.
I found retreat '09-'12 in the SW on app. 15000 km1 of the total 56000 km1 icesheet limit. It would correspond with app. 3000 km2.
The mean sheet thickness being 1400 m1, that area would correspond with 4000 km3.
The edge is a lot thinner than the mean thickness. But the equivalent melt extended over a much larger part of the sheet.

The minimum loss is hard to be imagined less than that of 2010 (500 km3), the maximum could even be as large as 1000 km3.

Can not find any references at this time by googling (probably asking wrong info), but I seem to remember seeing a program about the problems scientist are now having getting good quality ice cores in Greenland because the deterioration of the ice even at depths. Is this true and if so would not that signal the the ice fields are in even greater trouble then we can imagine?